In a lengthy, highly detailed article for Seeking Alpha, Richard Pearson, a private long-short investor known for conducting deep investigations into the marketing practices of small companies, writes that "the driving force behind Northwest Bio's share price has been a string of promotional articles from a variety of authors which have issued very bullish predictions for the stock."

(Seeking Alpha has labeled the article as a "Editor's Pick," a status reserved for work that the editors on the site consider to be of particularly high quality.)

Pearson contended that "many of the authors who have written on Northwest are using fake identities and fake credentials. They pretend to be biologists, other scientists, or fund managers. In fact, they are just paid writers."

Pearson said that he has a short position in Northwest Bio, though he wouldn't disclose the size of the position or when he took it. Shares of the company were down 5.3% on Monday, a day when the iShares Nasdaq Biotechnology ETF (
IBBIBB 1.9681960375391032%iShares Nasdaq Biotechnology ETFU.S.: Nasdaq273.805
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) was down by 2.6%.

But Northwest Bio CEO Linda Powers denied all the charges contained in the Seeking Alpha Piece. "Each of the major points about us are not accurate," she told Barrons.com Monday. "Pearson writes that the stock price has gone up because of promotion articles. Nowhere does he mention the real reason, that the company has made tremendous operational progress."

In these cases, editors at sites including Seeking Alpha, Wall Street Cheat Sheet, and Forbes.com, concluded that various freelance writers had misrepresented themselves.

The article purges underscore the challenges that many financial Websites face when they rely on articles submitted by armies of freelancers whose identities and intentions are often not fully understood at the time of publication.

The stocks involved in these promotions have mostly been biotechs since these shares are largely held by retail investors who tend to be more influenced by articles on Websites than institutional investors.

The latest company to be caught up in this running stock-promotion story is Northwest Bio, a $386 million market cap, clinical-stage biopharma company focused on the development of personalized cancer vaccines for various solid tumor cancers.

In his latest piece posted to Seeking Alpha Monday morning, Pearson wrote that since mid-2012, Northwest Bio has made use of an outside investor-relations firm called MDM Worldwide.

"Shortly after Northwest began paying MDM, the bullish articles began to appear from these fake authors," Pearson added.

He wrote that several writers on Northwest have a "broad and visible connection to MDM and / or to 'content' firm Redfish Creative, which has a relationship with MDM. Redfish has already provided me with pricing sheets outlining how much it charges for different types of (undisclosed) paid articles. Redfish has also laid out its techniques for (undisclosed) paid writing on message boards."

Pearson writes that he managed to get John Eastman, a principal at Redfish, to talk to him by pretending he was someone interested in writing favorable articles about stocks. He said that he didn't disclose his real identity since that would have ended the discussion.

Powers, Northwest Bio's CEO, confirmed that her company has a longstanding business relationship with MDM Worldwide. But she argues that the firm only helps her company with its Website and by promoting Northwest Bio on social media sites such as LinkedIn and doesn't commission freelance writers to do favorable articles, as Pearson alleges. Powers said that after reading Pearson's article, she reached out to MDM just to make sure that the company hadn't engaged writers to do promotion pieces on the biotech's behalf. She said that MDM confirmed that it hadn't.

She also added that principals with MDM have told her that the firm has never engaged Redfish to do any work for Northwest.

Reached for comment, Redfish's Eastman said that Pearson is "absurdly misinformed, draws totally incorrect conclusions from the scraps of data he has assumed in an apparent deceptive manner, all of which are unprofessional and misleading."

He added: "We do not pay writers to write favorable or unfavorable articles. There is no agenda to what we do."

Boris Peaker, a biotech analyst with Oppenheimer & Co. who follows Northwest Bio, hadn't read Pearson's article nor had he ever heard of him when contacted by Barrons.com on Monday afternoon. "I don't have any comment on the allegations," he said.

But Peaker, who has a "perform" or neutral rating on the stock, said that Northwest, like all biotechs, moves on short-term sentiment and its strong retail-investor base makes it a volatile play.